Field of the Invention
Embodiments of the present invention generally relate to a centralizer for use in wellbore operations. In particular, embodiments of the present invention relate to a centralizer having selectively expandable bow springs.
Description of the Related Art
Centralizers are used to center one tubular member inside a borehole or in another tubular member, e.g., to center a first smaller casing in a second larger casing. Typically centralizers are placed on the exterior of the inner casing and project outwardly therefrom. In many typical situations, the annular space between the outer circumference of the smaller casing and the inner circumference of the larger casing is sufficiently large that, with some force, a centralizer on the inner first casing can be moved into the interior of the second outer casing.
In a variety of situations, the centralizer may pass through a restriction in the wellbore that is smaller than the anticipated annular space. For example, the centralizer may be required to pass through seal bores in a wellhead. As it passes through the wellhead, the radial stand-off force of the bow springs may damage the surface of the bores.
There is a need, therefore, for a centralizer having selectively expandable bow springs.